Browse categories and answer follow-up questions to refine your symptom profile.
History
HPI overview
HPI overview
Affected joint
Time course
Single joint
Multiple joints
Recent trauma
Overuse
OPQRST
OPQRST
Onset
Sudden
Gradual
Provocation and palliation
Worse with weight bearing
Worse with passive range of motion
Relief with rest
Response to NSAIDs
Quality
Deep ache
Throbbing
Sharp with movement
Region and radiation
Primary joint location
Referred pain
Severity
Pain score
Functional limitation
Timing
Constant
Intermittent
Nocturnal pain
Associated symptoms
Associated symptoms
Fever
Chills
Malaise
Inability to bear weight
New rash
Dysuria
Sore throat
Infection exposure history
Infection exposures
Recent skin infection
Recent bacteremia
Recent dental work
Recent pneumonia
Recent urinary infection
Joint specific history
Joint specific history
Prior joint disease
Prior gout or pseudogout
Prior septic arthritis
Prior arthrocentesis
Recent intraarticular injection
Recent arthroscopy
Alarm Features
Resuscitation triggers
Resuscitation triggers
Suspected septic shock
Altered mental status
Respiratory distress
Persistent hypotension after fluids
Vital sign danger thresholds
Vital sign danger thresholds
Systolic blood pressure under 90 mmHg
Heart rate over 130
Respiratory rate over 30
Oxygen saturation under 92 percent on room air
Temperature 38.5 C or higher
High risk joint features
High risk joint features
Inability to tolerate passive range of motion
Rapidly progressive pain and swelling
Overlying cellulitis
Pain out of proportion
Neurovascular compromise distal to joint
High risk host features
High risk host features
Immunocompromised state
Prosthetic joint
Hemodialysis
Injection drug use
Recent surgery on the joint
Necrotizing infection concern
Necrotizing infection concern
Severe pain beyond exam findings
Crepitus
Bullae
Rapid skin discoloration
Medications
Current medications
Current medications
Antibiotics within past 7 days
Immunosuppressants
Systemic corticosteroids
Biologic agents
Disease modifying antirheumatic drugs
Anticoagulation and bleeding risk
Anticoagulation and bleeding risk
Warfarin
Direct oral anticoagulants
Antiplatelets
Known bleeding disorder treatments
Analgesics and antipyretics
Analgesics and antipyretics
NSAIDs
Acetaminophen
Opioids
Allergy history
Allergy history
Beta lactam allergy details
Vancomycin reaction history
Sulfonamide allergy
Diet
Recent intake and hydration
Recent intake and hydration
Poor oral intake
Dehydration signs
Recent vomiting
Recent diarrhea
Relevant exposures
Relevant exposures
Alcohol use
High purine intake pattern
Recent fasting
High fructose beverages
Review of Systems
Constitutional and infection
Constitutional and infection
Fever
Chills
Night sweats
Weight loss
Skin and soft tissue
Skin and soft tissue
Rash
New wound
Abscess
Cellulitis
Cardiopulmonary
Cardiopulmonary
Chest pain
Shortness of breath
Palpitations
Gastrointestinal and genitourinary
Gastrointestinal and genitourinary
Abdominal pain
Diarrhea
Dysuria
Urethral discharge
Neurologic
Neurologic
Headache
Neck stiffness
Focal weakness
New confusion
Collateral History and Family History
Collateral source
Collateral source
Family
Caregiver
EMS
Facility records
Family history
Family history
Inflammatory arthritis
Gout
Autoimmune disease
Sickle cell disease
Exposure history
Exposure history
Sick contacts
Recent travel
Animal bites
Tick exposure
Risk Factors
Septic arthritis risk factors
Septic arthritis risk factors
Age over 80
Rheumatoid arthritis
Diabetes mellitus
Chronic kidney disease
Cirrhosis
HIV
Procedure and device risks
Procedure and device risks
Prosthetic joint
Recent joint surgery
Recent arthrocentesis
Recent intraarticular steroid injection
Pathogen specific risks
Pathogen specific risks
MRSA risk
Prior MRSA colonization
Prior MRSA infection
Gonococcal risk
New sexual partner
Unprotected sex
Gram negative risk
Older age
Immunocompromised state
Pseudomonas risk
Injection drug use
Puncture wound through shoe
Bleeding and procedure safety
Bleeding and procedure safety
Anticoagulant use
Thrombocytopenia history
Liver disease
Differential Diagnosis
Life threatening
Life threatening
Septic arthritis (M00.9)
Fever or systemic toxicity
Severe pain with passive range of motion
Necrotizing soft tissue infection (M72.6)
Pain out of proportion
Crepitus or bullae
Osteomyelitis adjacent to joint (M86.9)
Persistent focal bone pain
Failure to improve with supportive care
Septic shock (R65.21)
Hypotension
Elevated lactate
Common
Common
Crystal arthritis
Gout (M10.9)
Prior flares
Hyperuricemia history
Pseudogout (M11.20)
Older age
Knee or wrist involvement
Traumatic hemarthrosis
Anticoagulant use
Recent injury
Cellulitis overlying joint (L03.90)
Warmth and erythema without effusion
Pain less with passive range of motion
Less common
Less common
Reactive arthritis (M02.30)
Recent gastrointestinal infection
Recent genitourinary infection
Inflammatory arthritis flare
Rheumatoid arthritis (M06.9)
Psoriatic arthritis (L40.50)
Lyme arthritis
Tick exposure
Large joint effusion with milder pain
Avascular necrosis (M87.00)
Steroid exposure
Sickle cell disease
Mimics and pitfalls
Mimics and pitfalls
Septic arthritis with afebrile presentation
Older age
Immunocompromised state
Crystal arthritis with fever and high CRP
Crystals do not exclude concurrent infection
Culture required when suspicion persists
Past Medical History
Relevant conditions
Relevant conditions
Diabetes mellitus (E11.9)
Chronic kidney disease (N18.9)
Cirrhosis (K74.60)
HIV (B20)
Sickle cell disease (D57.1)
Joint history
Joint history
Prosthetic joint details
Prior joint infections
Prior inflammatory arthritis diagnosis
Prior crystal proven gout or pseudogout
Recent infections and hospitalizations
Recent infections and hospitalizations
Recent bacteremia
Recent endocarditis
Recent ICU admission
Baseline function
Baseline function
Baseline ambulation
Baseline need for assistive devices
Baseline joint range of motion
Physical Exam
Initial appearance and vitals
Initial appearance and vitals
Toxic appearance
Hydration status
Fever pattern
Perfusion signs
Joint exam
Joint exam
Inspection
Swelling
Erythema
Deformity
Palpation
Warmth
Effusion
Focal tenderness
Range of motion
Pain with passive range of motion
Pain with active range of motion
Mechanical block
Comparison
Contralateral joint findings
Multiple joint survey
Neurovascular exam distal to joint
Neurovascular exam distal to joint
Distal pulses
Capillary refill
Sensation
Motor function
Skin and source evaluation
Skin and source evaluation
Cellulitis
Abscess
Wounds
Injection sites
Cardiac and pulmonary
Cardiac and pulmonary
New murmur
Signs of heart failure
Lung crackles
Respiratory distress
Abdominal and genitourinary
Abdominal and genitourinary
Abdominal tenderness
Costovertebral angle tenderness
Pelvic tenderness when relevant
Pediatric hip focus
Pediatric hip focus
Refusal to bear weight
Hip held in flexion and external rotation
Pain with gentle internal rotation
Lab Studies
Blood tests for systemic infection
Blood tests for systemic infection
CBC with differential
CRP
ESR
Blood cultures
Metabolic and organ function
Metabolic and organ function
Electrolytes and creatinine
Liver enzymes
Glucose
Sepsis evaluation when ill appearing
Sepsis evaluation when ill appearing
Lactate
Venous blood gas
Coagulation studies
Pregnancy and special populations
Pregnancy and special populations
Pregnancy test when applicable
HIV test when risk or unclear status
Sickle cell hemolysis markers when applicable
Synovial fluid analysis
Synovial fluid analysis
Appearance
Purulent
Bloody
Cell count with differential
WBC threshold interpretation
PMN percent interpretation
Gram stain
Low sensitivity in many cases
Positive result supports immediate targeted therapy
Culture
Aerobic and anaerobic
Reduced yield after antibiotics
Crystal analysis
Monosodium urate
Calcium pyrophosphate
Additional tests when indicated
Gonorrhea NAAT from genital sites
Synovial NAAT for gonorrhea when available
Interpretation pitfalls
Interpretation pitfalls
Normal WBC and normal CRP do not exclude early infection
Crystals present do not exclude concurrent infection
Prior antibiotics reduce culture yield
Imaging
Scoring Systems
Scoring systems
Kocher criteria for pediatric hip
Fever
Non weight bearing
ESR elevated
Serum WBC elevated
Modified Kocher additions
CRP elevated
Higher probability with more criteria
Limitations
Lower performance outside pediatric hip
Does not replace arthrocentesis when suspicion high
MRI
MRI
Indications
Suspected osteomyelitis
Suspected deep abscess
Persistent pain with unclear diagnosis
Contraindications
Non compatible implanted device
Severe claustrophobia without resources
Interpretation pearls
Adjacent bone marrow edema suggests osteomyelitis
Synovial enhancement supports inflammatory or infectious synovitis
CT
CT
Indications
Deep pelvic or sacroiliac joint concern
Alternative diagnosis evaluation
Limitations
Limited soft tissue contrast compared with MRI
Radiation exposure
Contrast considerations
Contrast allergy history
Renal function dependent use
Ultrasound
Ultrasound
Indications
Effusion detection
Arthrocentesis guidance
Interpretation pearls
Effusion supports intraarticular process
Absence of effusion does not exclude early infection
Pitfalls
Cellulitis can mimic effusion pain pattern
Small effusions can be missed without targeted views
Special Tests
Arthrocentesis and procedural diagnostics
Arthrocentesis and procedural diagnostics
Indications
Suspected septic arthritis
First episode of acute monoarthritis
Contraindications relative
Overlying cellulitis at needle entry site
Uncorrected severe coagulopathy
Technique considerations
Ultrasound guidance when available
Large bore needle for viscous fluid
Post procedure monitoring
Persistent bleeding at site
Worsening pain or swelling
Infectious source testing
Infectious source testing
Urinalysis and culture when urinary symptoms
Throat testing when pharyngitis symptoms
Skin and wound cultures when purulence present
Endocarditis evaluation when indicated
Endocarditis evaluation when indicated
New murmur
Positive blood cultures
Embolic phenomena
ECG
Indications in suspected septic joint
Indications in suspected septic joint
Tachycardia out of proportion
Chest pain or dyspnea
Electrolyte abnormalities
High risk patterns impacting management
High risk patterns impacting management
New ischemic changes
Atrial fibrillation with rapid ventricular response
Prolonged QT
Hyperkalemia patterns
Assessment
Working diagnosis and severity
Working diagnosis and severity
Suspected septic arthritis (M00.9)
Acute monoarthritis
Effusion with severe pain on passive range of motion
Elevated inflammatory markers when present
Sepsis severity stratification
Sepsis without shock
Septic shock
Key complications to rule out
Key complications to rule out
Bacteremia
Endocarditis
Osteomyelitis
Necrotizing soft tissue infection
Diagnostic uncertainty
Diagnostic uncertainty
Crystal arthritis overlap
Inflammatory arthritis flare overlap
Early infection with nondiagnostic labs
Plan
First 5 minutes
First 5 minutes
Cardiac monitor
Two large bore IV lines if toxic appearance
Oxygen if saturation under 92 percent
IV fluids if hypotension or poor perfusion
Diagnostic sequencing
Diagnostic sequencing
Arthrocentesis prioritized before antibiotics when stable
Blood cultures before antibiotics when febrile or toxic
Imaging for effusion localization when uncertain anatomy
Empiric antibiotics
Empiric antibiotics
Timing
If septic shock then antibiotics immediately after cultures
If stable then antibiotics after synovial fluid obtained
Typical adult empiric coverage
Vancomycin IV
Initial dose 15 to 20 mg per kg
Trough or AUC monitoring local protocol dependent
Ceftriaxone IV
2 g daily
Gram negative risk or immunocompromised
Cefepime IV
2 g every 8 to 12 hours renal adjustment required
Piperacillin tazobactam IV
4.5 g every 6 to 8 hours renal adjustment required
Gonococcal concern
Ceftriaxone IV or IM
1 g daily
Doxycycline PO
100 mg twice daily for 7 days when chlamydia not excluded
Beta lactam anaphylaxis
Vancomycin IV
Aztreonam IV
2 g every 8 hours renal adjustment required
Source control and consultation
Source control and consultation
Orthopedics consultation
Suspected septic arthritis
Prosthetic joint
Infectious diseases consultation
Bacteremia
Unusual pathogens
Operative washout triggers
Hip involvement
Shoulder involvement
Failure of serial aspirations
Analgesia and supportive care
Analgesia and supportive care
Acetaminophen PO or IV
1000 mg every 6 to 8 hours
Maximum 3000 mg per day in many adults
NSAID when appropriate
Ibuprofen PO
400 mg every 6 to 8 hours
Contraindications
CKD
GI bleeding risk
Opioid for severe pain
Morphine IV
0.05 mg per kg
Repeat every 10 to 15 minutes to effect
Reassessment loop
Reassessment loop
Vitals every 30 to 60 minutes if ill appearing
Pain and range of motion trend
Perfusion and mental status trend
Culture and Gram stain updates
Disposition
Admission criteria
Admission criteria
Suspected septic arthritis
Positive Gram stain
Synovial culture pending with high suspicion
Sepsis physiology
Immunocompromised state
ICU criteria
ICU criteria
Vasopressor requirement
Lactate persistently elevated
Worsening respiratory status
Altered mental status
Transfer criteria
Transfer criteria
Need for urgent orthopedic surgery not available
Pediatric hip suspected septic arthritis
Prosthetic joint infection requiring specialty service
Discharge criteria when septic arthritis ruled out
Discharge criteria when septic arthritis ruled out
Alternative diagnosis established
Stable vital signs
Pain controlled on oral regimen
Reliable follow up within 24 to 72 hours
Observation pathway criteria
Observation pathway criteria
Low suspicion after aspiration and labs
Pending cultures with close reassessment plan
No systemic illness
Discharge Instructions
Copy discharge instructions
Copy discharge instructions
Today you were evaluated for joint pain and swelling
A serious joint infection can worsen quickly and can damage the joint
Return to the emergency department now if any of the following occur
Fever
Increasing pain
Increasing swelling
New redness spreading
New inability to walk or use the joint
New weakness or numbness
New confusion
Medications
Take pain medicines exactly as prescribed
Avoid NSAIDs if you were told you have kidney disease or stomach bleeding risk
Activity
Rest the joint
Avoid weight bearing until symptoms improve unless told otherwise
Follow up
Follow up with your clinician within 24 to 72 hours
If cultures were sent you may be contacted with results and treatment changes
References
Guidelines and key sources
Guidelines and key sources
Infectious Diseases Society of America guideline for MRSA infections 2011
American Academy of Orthopaedic Surgeons clinical practice guidance for diagnosis and management of periprosthetic joint infection 2019
European Bone and Joint Infection Society guidance on septic arthritis in native joints 2023
Centers for Disease Control and Prevention sexually transmitted infections treatment guidelines 2024
American College of Rheumatology gout management guideline 2020
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.